Hi Everyone, I'm CC'ing Mark Rogers who, upon looking at the Author of Boost.Functional (and I assume is the maintainer) may be able to help out with this regard. Recently, I've implemented a simple utility which allows users to select the nth element of an STL pair / Boost.Tuple in conjunction with STL algorithms. This allows precisely the following usage semantics: std::map<int, int> int_map; int_map[0] = 1; int_map[1] = 2; std::transform(int_map.begin(), int_map.end(), std::ostream_iterator<int>(std::cout, " "), boost::select<1>()); // output: "1 2 " This is a generalization of the SGI select1st and select2nd function objects. It also works with a container of Boost.Tuple's: std::list<boost::tuple<double, double, double> > coord_list; coord_list.push_back(boost::make_tuple(1.0, 2.0, 3.0)); coord_list.push_back(boost::make_tuple(4.0, 5.0, 6.0)); std::transform(coord_list.begin(), coord_list.end(), std::ostream_iterator<double>(std::cout, " "), boost::select<0>()); // output "1.0 4.0 " I've re-attached the implementation, for comments and review for inclusion in Boost.Functional. Thanks very much, and I hope to hear from you guys soon. -- Dean Michael C. Berris Software Engineer, Friendster, Inc. [http://cplusplus-soup.blogspot.com/] [mikhailberis@gmail.com] [+63 928 7291459] [+1 408 4049523]